The invention is based on a fuel injection valve for internal combustion engines as generically defined by the preamble to claim 1.
One such fuel injection valve is known from German patent disclosure DE 198 13 983 A1. This fuel injection valve is a component part of a reservoir-type fuel injection system and has an injection valve member by which at least one injection opening is controlled and which has a pressure shoulder that defines a pressure chamber. Fuel under pressure can be delivered to the pressure chamber from a high-pressure fuel source via a pressure line, by which fuel the injection valve member can be lifted from a valve seat counter to a closing force to open the at least one injection opening. The motion of the injection valve member is varied by a control valve that has a piezoelectric actuator-actuated control valve member, which controls a pressure, prevailing in a control pressure chamber that communicates with a pressure source, that urges the injection valve member in its closing direction. By means of the control valve member, the control pressure chamber can be made to communicate with a relief chamber, and as a result the pressure in the control pressure chamber drops, and the injection valve member can be moved in the opening direction. The motion of the control valve member by means of the piezoelectric actuator must take place counter to the pressure prevailing in the control pressure chamber, so that moving the control valve member entails a major expenditure of force.
The fuel injection valve of the invention as defined by the characteristics of claim 1 has the advantage over the prior art that the motion of the control valve member for connecting the control pressure chamber to the relief chamber need not take place counter to the pressure in the control pressure chamber, and thus only slight force is required to move the control valve member. This makes it possible to use a piezoelectric actuator of slight dimensions, and thus the structural size and the weight of the control valve can be kept small and low, respectively. Furthermore, by means of the control valve member, the opening stroke of the injection valve member can be limited in an infinitely graduated way.
Advantageous features and refinements of the fuel injection valve of the invention are defined by the dependent claims. By means of the embodiment defined by claim 2, secure closing of the conduit at the closing piston by the control valve member is achieved, if the piezoelectric actuator is not activated. By means of the spring provided in accordance with claim 3, the force the piezoelectric actuator must exert to move the control valve member counter to the restoring spring is reduced.
One exemplary embodiment of the invention is shown in the drawing and described in further detail below. FIG. 1 shows a reservoir-type fuel injection system in schematic fashion, and FIG. 2 shows a fuel injection valve of the reservoir-type fuel injection system in a longitudinal section.